Microbiological analyses of 716 seafood samples over a 3-year period revealed that the microbiological quality of fresh seafood in North Carolina was generally acceptable. The mean aerobic counts (APC) and fecal coliform counts were low as was the occurrence of enteric pathogens, except for Vibrio parahaemolyticus and coagulase-positive staphylococci. Salmonella species were isolated from three samples, but the fecal coliform counts of these samples far exceeded the shellfish standard of the United States Food and Drug Administration. Coagulase-positive staphylococci were isolated in low numbers from nearly all the different types of seafoods; unpasteurized crabmeat and head-peeled shrimp samples showed the highest counts (10% of these samples had numbers which exceeded 100/g). V. parahaemolyticus occurred frequently in fresh seafood (overall 46% of the samples were positive) and its numbers showed a definite seasonal variation. No positive statistical correlation was found between the numbers of V. parahaemolyticus and the bacteriological indices, such as coliforms, fecal coliforms, enterococci and APC. Processing practices were found to influence the occurrence of V. parahaemolvticus in seafood; for example, improperly cleaned flumes were found to be a reservoir for V. parahaemolyticus in mechanical scallop processing plants. Also ‘picking’ waste ‘containers’ were found to be sources of V. parahaemolyticus in crab processing plants. Some processing practices such as heat shocking of oysters to facilitate opening were found to reduce the numbers of V. parahaemolyticus . Fifty V. parahaemolyticus isolates from different seafoods were tested for their Kanagawa reaction and all were found to be negative.

Yogurt customarily contains large numbers of viable starter culture, although some yogurt is heat-treated to inactivate the starter. It was found that heating to inactivate the starter also inactivated lactase. This could have a disadvantageous effect on lactose-intolerant consumers. Manufacture of frozen yogurt did not have any appreciable damaging effect on the yogurt culture or lactase activity.

Increased use of lactobacilli as dietary supplements has emphasized the need for preparations of those cultures that possess the attributes of cell viability. resistance to bile and capability of establishing in the intestinal tract. Incompatibility of different species of lactobacilli may limit development of products designed to overcome objectionable, or impart improved flavor to cultured foods. Stresses that are imposed on cultures during their preparation and distribution must minimize damage to cells which would detract from the foregoing characteristics.

Pasteurized low fat milk to which is added Lactobacillus acidophilus has now become a product of major volume on the U.S. market. The product contains millions of L. acidophilus per ml and is considered to be in the general category of cultured milk products for application of regulatory monitoring. There is a growing interest in developing standards for allowable minimum numbers of L. acidophilus in such products at point of sale. This can be accomplished best by use of a medium selective for lactobacilli such as Lactobacillus Selection Agar (LBS); non-selective media, such as APT agar, can also be used to enumerate L. acidophilus . The latter would provide less assurance that the counts were due to lactobacilli. The non-selectivity of APT, however, usually results in higher counts of L. acidophilus . There is need for application of accurate monitoring of such products to ensure the numbers as well as the identity of the culture used as the milk supplement.

Lactobacillus acidophilus exerted antagonistic actions on growth of Staphylococcus aureus , Salmonella typhimurium , enteropathogenic Escherichia coli , and Clostridium perfringens when grown with each in associative cultures. S. aureus and C. perfringens were more sensitive to the inhibition than were S. typhimurium and E. coli . The amount of the antagonism produced varied among strains of L. acidophilus and could not be directly related to amounts of acid produced; hydrogen peroxide produced by the lactobacilli appeared to be partially responsible for the antagonistic interaction. The inhibitory effect was produced also under anaerobic conditions in a pre-reduced medium.

A medium was developed for selectively enumerating bile-resistant lactobacilli by adding 0.15% oxgall to lactobacillus selective agar (BBL). Lactobacilli were not found in many products sold as sources of Lactobacillus acidophilus , whereas others contained widely different numbers of lactobacilli capable of forming colonies on the bile medium. Of seven products from which lactobacilli were isolated, only three contained L. acidophilus . One of these products was from a pharmacy and the other two were from dairy processor(s).

The fate of bacteria contained in food during freezing, storage, and thawing is usually one that is detrimental. However, many microorganisms considered to have been killed by such treatments actually are only injured. Their viability can be determined by allowing the injury to repair in a non-selective medium before testing for their presence on selective media. Injured cells of pathogens have been found to be as pathogenic as uninjured ones; injured spoilage microorganisms can cause spoilage if permitted to repair and grow. Injured microorganisms and their potential importance in food safety and shelf-life constitute and important problem for the frozed food industry as well as the food sanitarian.

Concentrated starter cultures are now used routinely in many food fermentations. Recent literature concerning preparation and performance of such cultures is reviewed. Batch procedures are preferred over continuous culture procedures for preparing concentrated cultures. Most attention has been focused on bacteria used to manufacture cultured milk products. Performances of concentrated cultures of lactic streptococci, leuconostocs, lactobacilli, and thermophilic streptococci in preparing cultured dairy products have compared favorably to those of traditionally prepared milk cultures. Storage in liquid nitrogen appears to be the best method for long term holding of concentrated cultures.

The lactic streptococci have been utilized to produce certain fermented foods for many years. In addition to producing a cultured food having new characteristics, these organisms aid in preserving the food. Growth of salmonellae and staphylococci is retarded in foods cultured with lactic streptococci. This antagonistic action is caused by factors in addition to the acidic environment created by the streptococci since pathogens can be repressed even when the milk is maintained at pH 6.6 during starter growth. The intensity of the antagonistic action cannot be predicted by the rate at which acid is produced by the streptococci.

Methodology for detection and enumeration of microorganisms has involved an increasing awareness of the role of cellular injury on analytical microbiology. Injury has been shown to result from heat, freezing, chemicals, irradiation, and similar treatments. All of these treatments are commonly used in the processing and preservation of foods. Since injured microorganisms can recover and cause food spoilage or since injured pathogens can recover and become infective, the detection of injured pathogens or of injured index microorganisms is imperative in order to assure the safety of foods. The detection of injured microorganisms becomes more difficult with the use of selective media. Environmental conditions or added inhibitors which are used to allow only the development of the types being sought may exert unsuspected inhibition. This shortcoming in our methodology appears to occur in the use of selective media in quantitative determinations, as well as in enrichment media that are designed to promote the growth and easier qualitative detection of a specific pathogen or indicator organism. One of the most pressing problems facing the food microbiologist at this time appears to be means to resuscitate an injured microorganism so that it can be detected selectively in the quantitative or qualitative examination of foods.

In a field study covering 15–16 months and which involved 155 Grade A milk producers in three widely separated areas, a detergent-sanitizer was compared with customary methods of milk utensil sanitization. No supervision was made of the producers other than that normally given by the sanitarian and fieldman. Bacterial counts, thermoduric and total, tended to be lower in the milk from producers using the detergent-sanitizer sanitization procedure. Milking utensils appeared cleaner and, milk-stone deposits were absent from the utensils of those producers who used the detergent-sanitizer method. Since this study covered an extended period of time with only normal supervision of the producers, the detergent-sanitizer method appears to be one that can be used routinely over an indefinite period of time with entirely satisfactory results.

In a field study involving 26 Grade A milk producers a detergent-sanitizer was compared with the customary method of cleaning and sanitizing milking equipment. The producers were divided into two comparable groups and placed on a double-reversal trial with three 5-week periods. Milking utensils appeared cleaner and milk-stone deposits were reduced when the detergent-sanitizer was used in place of the regular procedure. The difference between the two methods of cleaning and sanitizing utensils was not statistically signifcant as measured by thermoduric and total bacterial counts. The relation between the effectiveness of the detergent-sanitizer and the hardness of water was not statistically significant. There was no appreciable amount of quaternary ammonium compound in any of the milk samples as determined by direct measurement and by the activity of a buttermilk culture.